1. Field of the Invention
The present invention relates generally to the field of petroleum production processes. More specifically, the present invention relates to the economic manufacture of a working fluid composed mainly of liquefied CO2, but including other acceptable impurities, for use in enhanced production of oil or natural gas from underground formations also known as enhanced oil recovery (EOR) or enhanced gas recovery (EGR) respectively. This invention also relates generally to the use of this new mechanism for the production of the EOR and EGR working fluid specifically for the EOR or the EGR operations.
2. Description of the Related Art
Crude oil is generally extracted from petroleum reservoirs in three successive phases: primary recovery, secondary recovery, and tertiary recovery. Crude oil is recovered in the primary recovery phase through an extraction process which makes use of natural pressure, gravitational forces, drilling and pumping to lift the crude oil to the surface.
The secondary production phase, or secondary recovery, makes use of liquid displacement techniques such as water flood techniques, to force crude oil to the surface.
Tertiary production, also known as enhanced oil recovery (EOR), makes use of thermal, chemical or gaseous injections into oil-bearing stratum to force crude oil from subterranean production reservoirs. CO2 gas injections account for about half of the EOR operations currently ongoing in the United States. As oil production fields mature, EOR is increasingly the technique of choice to improve crude oil production from declining petroleum reservoirs.
Most CO2 used in EOR originates in natural underground reservoirs. These natural CO2 reservoirs are generally not located near oil producing basins, necessitating the construction of pipelines to carry liquefied CO2 long distances from remote CO2 production areas to the EOR fields where the CO2 is needed.
Some anthropogenic sources of CO2 are used as CO2 production sources. These sources include fertilizer production and synthetic natural gas production operations, from which CO2 can be captured The production of CO2 EOR streams from power generation plants has been proposed, but significant technological and economic barriers exist with the technologies that have to date been investigated.
Enhanced gas recovery (EGR) makes use of the same techniques as EOR but with the goal of recovering gases, such as natural gas, rather than petroleum crude. EGR has not generally been found to be economical in light of the costs associated with the production of such gas exceed the value of the petroleum gas derived, because, inter alia, once CO2 begins to re-circulate from injection into EGR production the cost of processing the CO2 out of such EGR produced gas again reduces the economic viability of EGR production.